Differences in the velocity distribution functions Δf(v_⊥, v_∥) between the final (ω_pt = 1200) and the initial state (ω_pt = 0) for an increasing value of the characteristic thermal velocity v_th (rows). The dashed lines represent resonance curves for gyro-harmonic numbers s = 12, 13, 14, 15, with s = 12 being closest to zero velocity. Arrows denote shifts in the VDF contained within the resonance curves.